- May be elevated when CRP is normal, useful in distinguishing between IBD and IBS and for subsequent monitoring.
Stool Microscopy, Culture and Examination
- For clostridium difficile toxin, or for ova or cysts; if admitted three separate stool samples should be analysed for sensitivity.
- May show anaemia due to vitB12 malabsorption/bleeding.
- May be lower due to protein-losing enteropathy, inflammation or poor nutrition/malabsorption.
ESR and CRP
- Elevated in exacerbations and in response to abscess formation.
- Does not involve exposure to radiation.
- Sensitive way of detecting extra-intestinal manifestations and of assessing pelvic and perineal involvement.
- Studies use an oral small bowel-distending agent and IV contrast to provide transmural imaging that can usefully distinguish between predominantly inflammatory strictures (that should respond to anti-inflammatory medical strategies) and fibrotic strictures (that require a mechanical solution, such as surgical resection, stricturoplasty or endoscopic balloon dilatation).
- Essential in the management of patients who present with severe active disease. Dilatation of the colon, mucosal oedema (thumb-printing) or evidence of perforation may be found. In small bowel Crohn's disease, there may be evidence of intestinal obstruction or displacement of bowel loops by a mass.
- Very powerful tool to detect small bowel inflammation and stricture formation, but it is operator-dependent.
- Limited to screening for complications, such as perforation or abscess formation, in the acutely unwell.
- Patchy inflammation, with discrete, deep ulcers, strictures and perianal disease (fissures, fistulae and skin tags), is typically observed, often with rectal sparing. In established disease, colonoscopy may show active inflammation with pseudopolyps or a complicating carcinoma.
- Should be taken from each anatomical segment (terminal ileum, right colon, transverse colon, left colon and rectum) to confirm the diagnosis and define disease extent, and also to seek dysplasia in patients with long-standing colitis.
- May be required to make a histological diagnosis of small bowel Crohn's disease, when the inflamed segment is out of reach of standard endoscopes.
- All children and most adults with Crohn's disease should have upper gastrointestinal endoscopy and biopsy to complete their staging. Not only is upper gastrointestinal Crohn's disease relatively common, but it may help to make a definitive diagnosis in patients who otherwise appear to have non-specific colonic inflammation.